Battery pack identification scheme for power tool systems

ABSTRACT

A method is provided for identifying a battery pack that is operably coupled to a battery charger. The method comprises: measuring voltage at a plurality of designated terminals of a first battery pack while the battery pack is coupled to the battery charger; determining how many of the designated terminals are connected to a reference voltage, such as battery positive; and identifying an attribute of the battery pack based on how many of the designated terminals are connected to the reference voltage.

CROSS-REFERENCE TO RELATED APPLICATIONS

This continuation application claims the benefit of U.S. Non-Provisionalapplication Ser. No. 13/080,787 filed on Apr. 6, 2011 now U.S. Pat. No.8,653,787 and U.S. Provisional Application No. 61/321,699 filed on Apr.7, 2010. The disclosure of the above applications is incorporated hereinby reference.

FIELD

The present disclosure relates to an improved identification scheme forbattery packs in a power tool system.

BACKGROUND

Cordless products or devices which use rechargeable batteries areprevalent in the marketplace. Rechargeable batteries may be used innumerous devices ranging from computers to power tools. Since thedevices use a plurality of battery cells, the battery cells are commonlypackaged in a battery pack. The battery pack may in turn be used topower the devices when coupled thereto. Once depleted, the battery packmay be recharged by a battery charger.

Typically, a battery charger can only charge a specific type of batterypack as the terminal arrangement amongst different types of batterypacks vary. For example, a 20 volt battery pack may have a differentterminal arrangement than a 14 volt battery pack. It is appreciated thatthese two different battery packs may require two different batterychargers. One way to avoid the need for multiple battery chargers is tocreate a standard interface between different types of battery packs. Inthis way, it may be feasible to charge each of the different types ofbattery packs using the same battery charger. To ensure a propercharging algorithm is applied to battery packs having differentattributes, the battery charger needs to accurately identify the type ofbattery pack that is coupled to the battery charger. Therefore, it isdesirable to develop an improved identification scheme amongst batterypacks that couple to the same battery charger.

The statements in this section merely provide background informationrelated to the present disclosure and may not constitute prior art.

SUMMARY

In one aspect of the disclosure, a method is provided for identifying abattery pack that is operably coupled to a battery charger. The methodcomprises: measuring voltage at a plurality of designated terminals ofthe battery pack while the first battery pack is coupled to the batterycharger; determining how many of the designated terminals are connectedto a reference voltage, such as a positive battery terminal; andidentifying an attribute of the battery pack based on how many of thedesignated terminals are connected to the reference voltage. At leastone of the designated terminals is preferably connected to a nodedisposed between two of the battery cells in the battery pack.

In another aspect of the disclosure, a method is presented foridentifying a battery pack coupled to a battery charger. The methodincludes: measuring voltage at a plurality of designated terminals ofthe battery pack while the battery pack is coupled to the batterycharger; determining location of a given terminal amongst the designatedterminals; and identifying an attribute of the battery pack based on thelocation of the given terminal amongst the designated terminals.

In a further aspect of the disclosure, a battery pack for a portabletool includes a body having opposed first and second side walls orientedperpendicular to a body rear face. A body front face is oppositelydirected with respect to the rear face. A finger notch includes anengagement wall and an oppositely positioned lead-in wall. Theengagement wall and the lead-in wall are joined at a notch cavity bottomwall recessed within the body below the front face. The engagement wallhas a first pitch angle with respect to the front face and the lead-inwall has a second pitch angle with respect to the front face smallerthan the first pitch angle.

In yet another aspect of the disclosure, a battery pack connectionsystem includes a printed circuit board connection member. A connectoris mounted to the printed circuit board connection member and has atleast one aperture. At least one biasing member having a spring leg ispositioned in the at least one aperture. At least one cell wire has aconnection end. An electrical connection is created by insertion of theconnection end into the at least one aperture. The electrical connectionmaintained by a first biasing force created by elastic deflection of theconnection end in a first direction by direct contact with the at leastone biasing member such that the first biasing force acts in a seconddirection opposite to the first direction, and a second biasing forcecreated by elastic deflection of the spring leg in the second directionfrom direct contact between the connection end and the at least onebiasing member such that the second biasing force acts in the firstdirection. The spring leg and the connection end each have a differentspring constant, or the same spring constant but different masses.

Further areas of applicability will become apparent from the descriptionprovided herein. It should be understood that the description andspecific examples are intended for purposes of illustration only and arenot intended to limit the scope of the present disclosure.

DRAWINGS

FIG. 1 is a diagram of an exemplary system of power tools;

FIG. 2 a block diagram of an exemplary configuration for a batterycharger that operably couples to different types of battery packs;

FIG. 3 is a flowchart illustrating an exemplary charging schemeaccording the present disclosure;

FIGS. 4A-4C are diagrams of exemplary terminal arrangements for threedifferent types of battery packs;

FIG. 5 is a flowchart illustrating an exemplary method for identifying abattery pack coupled to a battery charger;

FIG. 6 is a flowchart illustrating another exemplary method foridentifying a battery pack coupled to a battery charger;

FIG. 7 is a front right perspective view of an embodiment of a batterypack having a female recessed finger notch;

FIG. 8 is a top plan view of the battery pack of FIG. 7;

FIG. 9 is a cross sectional side elevational view taken at section 9 ofFIG. 8;

FIG. 10 is a top plan view of another embodiment of a battery packconnection system having double-biased wire connectors;

FIG. 11 is a side elevational view of the battery pack of FIG. 10;

FIG. 12 is a top plan view of a further embodiment of a battery packconnection system having opposed biasing members; and

FIG. 13 is a cross sectional side elevational view taken at section 13of FIG. 12.

The drawings described herein are for illustrative purposes only ofselected embodiments and not all possible implementations, and are notintended to limit the scope of the present disclosure. Correspondingreference numerals indicate corresponding parts throughout the severalviews of the drawings.

DETAILED DESCRIPTION

The present disclosure can relate to a system of power tools of the typethat is generally indicated by reference numeral 10 in FIG. 1. Thesystem of power tools 10 can include, for example, one or more powertools 12, one or more battery packs 16 and a battery pack charger 18.Each of the power tools 12 can be any type of power tool, includingwithout limitation drills, drill/drivers, hammer drill/drivers, rotaryhammers, screwdrivers, impact drivers, circular saws, jig saws,reciprocating saws, band saws, cut-off tools, cut-out tools, shears,sanders, vacuums, lights, routers, adhesive dispensers, concretevibrators, lasers, staplers and nailers. In the particular exampleprovided, the system of power tools 10 includes a first power tool 12 aand a second power tool 12 b. For example, the first power tool 12 a canbe a drill/driver similar to that which is described in U.S. Pat. No.6,431,289, while the second power tool 12 b can be a circular sawsimilar to that which is described in U.S. Pat. No. 6,996,909. A batterypack 16 can be selectively coupled to either of the first and secondpower tools 12 a and 12 b to provide electrical power thereto. It isnoteworthy that the broader aspects of this disclosure are applicable toother types of battery powered devices.

FIG. 2 illustrates an exemplary configuration of a battery charger 18that operably couples to a plurality of different battery packs 16. Thebattery charger 18 is generally comprised of a power supply circuit 22(i.e., current source), a voltage monitoring circuit 23 and a chargercontrol module 24. The exemplary configurations are merely provided as acontext for describing the identification scheme disclosed herein.Moreover, the configuration may represent only a portion of the internalcircuitry. The battery pack and/or the battery charger may includeadditional functionality or components such as other identificationcomponents, protection circuits and/or other internal components whichare not shown herein for reasons for clarity.

The charger control module 24 is responsible for charging the batterycells and monitoring any fault conditions which may develop duringcharging. In an exemplary embodiment, the charger control module 24 isimplemented as software (processor-executable instructions) on a digitalmicrocontroller. However, the charger control module 24 may be embodiedin hardware or software as a digital microcontroller, a microprocessoror an analog circuit, a digital signal processor or by one or moredigital ICs such as application specific integrated circuits (ASICs),for example. It is also contemplated that a portion of the chargercontrol could reside in the battery pack.

To charge a battery pack 16, the pack 16 is operably coupled to thebattery charger 18. Various techniques for detecting the presence of thebattery pack may be employed. Upon detecting the battery pack 16, thebattery charger 18 initiates a charging scheme. In an exemplary chargingscheme, the charger 18 delivers a constant current to the battery pack16. When the stack voltage, an individual cell or a portion of the cellsreaches a target charging value, the charger 18 switches from a constantcurrent mode to a constant voltage mode. The charger 18 continuescharging in constant voltage mode until the charge current drops below apredefined threshold (e.g., 100 mA) at which time the charge current isterminated.

FIG. 3 illustrates another exemplary charging scheme which may beimplemented by the charger control module 24 of the charger 18. In thisscheme, the battery charger 18 begins by delivering a charge current 31to the battery pack. The charge current may be set at a maximum valuewhich can be delivered by the charger (e.g., 3 amps) or some lesservalue. In some embodiments, the charge current may be delivered inperiodic charge cycles (e.g., cycles of one second duration); whereas,in other embodiments, the charge current is delivered in continuously.

Cell voltages are continually being monitored at step 32 via the voltagemonitoring circuit 23 during the charging process. In the exemplaryembodiment, the cell voltage measurements can be made between chargecycles by the voltage monitoring circuit 23. The voltage monitoringcircuit 23 is preferably configured to take individual cell measurementsin a sequential manner during a span, e.g., of about 10-70 milliseconds.Individual cell measurements are in turn reported to the charger controlmodule 24 for further assessment. In the case that the charge current isdelivered continuously, cell voltage measurements are taken while thecharge current is being delivered to the battery cells.

The maximum charge current will continue to be delivered to the batterypack until at least one of the battery cells reaches a target chargingvalue (e.g., 4.15 volts) as indicated at step 33. When one or more ofthe battery cells reaches the target charging value, the charge currentwill be lowered. In an exemplary embodiment, the charge current islowered in predefined increments at step 38 until it reaches a minimumcharge current (e.g., 200 mA) that can be output by the charger. Forexample, the charge current may be reduced in half although otherdecrements are also contemplated.

The average charge current delivered to the battery cells may be loweredfurther by skipping charge cycles. When the charger is outputting aminimum charge current and less than all of the cells have reached thetarget charge value, charge cycles are skipped at step 39 to furtherlower the average charge current delivered to the cells. For example,skipping every other charge cycle further reduces the average chargingcurrent being delivered by the charger by 50% (e.g., from 200 mA to anaverage of 100 mA).

After each charge cycle, cell measurements are taken and a determinationis made as to whether to lower the charge current. In the exemplaryembodiment, the determination to lower the charge current is made by thecharger control module 24. In response to this command, the chargercontrol module 24 interfaces with the power supply circuit 22 to lowerthe charge current being delivered by the charger. When all of thebattery cells have reached the target charge value, the charge currentis terminated as indicated at step 35. This charging scheme isparticularly suitable for battery packs having cell balancingfunctionality. Other types of charging schemes are contemplated withinthe broader aspects of this disclosure.

The battery charger 18 may be configured to charge different types ofbattery packs 16. For example, the battery packs 16′, 16″, 16′″ may havedifferent number of battery cells and nominal voltage ratings, such a 12volt, 14.4 volt, and 20 volt, respectively. In each case, the batterypack 16 includes a plurality of battery cells 20 connected in series (asshown), or multiple strings of cells connect in parallel with oneanother in which the cells in a given string are connect in series witheach other. The number of serially-connected cells determines thenominal voltage rating for the battery pack. It is readily understoodthat other voltage ratings fall within the scope of this disclosure. Forpurposes of describing the exemplary embodiments, the battery pack 16may be composed of cells having lithium-ion cell chemistry. Likewise, itis understood that the battery pack 16 may be composed of cells ofanother lithium-based chemistry, such as lithium metal or lithiumpolymer, or another chemistry such as nickel cadmium (NiCd), nickelmetal hydride (NiMH) and lead-acid, for example.

The battery packs 16 may further include a temperature sensor 25. Thetemperature sensor 25 is configured to measure the temperature of thebattery cells. The temperature sensor 25 is in turn connected via aterminal to battery control module 24 when the battery pack 16 isoperably coupled to the battery charger 18. The temperature sensor 25may be implemented with a negative temperature coefficient (NTC)thermistor, a positive temperature coefficient (PTC) thermistor,temperature sensing integrated circuits, thermocouples, or othertemperature sensitive components. Other types of protection circuits mayalso be incorporated into the battery packs.

FIGS. 4A-4C illustrate exemplary terminal arrangements for three batterypacks 16′, 16″, 16′″ having different numbers of battery cells.Depending on cell chemistry and manufacturer, each battery pack willhave a different nominal voltage rating, e.g., 12 volt, 14.4 volt, and20 volt, respectively. In this exemplary embodiment, each battery packincludes eight terminals that engage electrical contacts of the batterycharger. Four of the terminals are the same amongst the three packs: apositive voltage terminal (B+), a negative voltage terminal (B−), athermistor terminal (Th) and a secondary identification terminal (ID).The remaining four terminals 19 enable voltage measurements to be takenbetween the battery cells in the battery pack at a measurement node 21.In the 20 volt battery pack 16′″, there are five battery cells connectedin series and thus four measurement nodes 21 are interspersed betweenthe five cells as best seen in FIG. 2. In this case, each measurementnode 21 is connected to one of the four remaining terminals 19 (alsoreferred to herein as designated terminals), thereby enabling thebattery charger to determine individual cell voltages of each cell 20 inthe battery pack 16′″. In the 14.4 volt battery pack 16″, there are fourbattery cells 20 and thus three measurement nodes 21 connected to threeof the four remaining terminals 19 such that one terminal 19 is unused.In the 12 volt battery pack 16′, there are three battery cells 20 andthus two measurement nodes 21 connected to two of the four remainingterminals 19 such that two terminals 19 are unused. Thus, there is atleast one of the designated terminals 19 in each of the battery packsconnected to a measurement node 21 disposed between two of the batterycells 20 in the battery pack 16. It is readily understood that theterminal arrangement can include more or less terminals and theterminals may serve other functions. It is further noted that voltagesshown in FIGS. 4A-4C are merely exemplary and provided to helpunderstand the identification schemes discussed below.

Prior to charging a given battery pack 16, the battery charger 18identifies the type of battery pack that is coupled thereto as shown inFIG. 5. In one exemplary identification scheme, the charger 18identifies the battery pack based upon the number of terminals 19connected to a reference voltage 23. With continued reference to thebattery packs 16 described above, unused terminals in battery packs 16′and 16″ can be tied to a battery reference voltage 23 as best seen inFIG. 2. More specifically, the unused terminals are connected to thepositive voltage terminal (B+) of the battery pack 16. In this way, theunused terminals 19 can be used to identify the battery pack. Otherreference voltages are contemplated by this disclosure.

To identify the pack type, the charger control module 24 first measuresvoltage at step 51 at a plurality of designated terminals (e.g.,terminals 3, 4, 6 and 7) of the battery pack. Given the voltagemeasurements for each terminal 19, the charger control module determinesat step 52 how many of the designated terminals 19 are connected to thebattery reference voltage. In this example, designated terminals 19 areconnected to the positive battery voltage (B+). The type of battery packcan then be determined based on the number of designated terminals 19that are connected to the reference voltage, e.g., in the manner setforth below.

In the exemplary embodiment, when the charge control module 24determines at 53 that only one of the terminals is connected to B+(ornone of the designated terminals 19), the battery charger is presumed tobe coupled to the pack 16′″ having five battery cells. The chargecontrol module 24 in turn selects a charging algorithm at step 54suitable for charging the identified battery pack 16′″. Alternatively,the charge control module 24 may set parameters (e.g., an overchargevoltage threshold for the total pack) in a generic charging algorithmthat is suitable for the identified battery pack 16′″. The chargecontrol module 24 can then interact with the power supply circuit 22 tocommence charging at step 59 in accordance with the appropriate chargingalgorithm.

When the charge control module 24 determines at step 55 that twoterminals are connected to B+ (or one designated terminal 19, i.e.,terminal 3), the battery charger 18 is presumed to be coupled to thebattery pack 16″ having four cells. When the charge control module 24determines at step 57 that three terminals are connected to B+ (or twodesignated terminals, i.e., terminals 3 and 6), the battery charger 18is presumed to be coupled to the battery pack 16′ having three cells. Ineither case, the charge control module 24 selects the appropriatecharging algorithm 56, 58 for the identified battery pack and commencescharging as indicated at step 59. It is readily understood that thecharging algorithms selected can vary for the different pack types. Itis further envisioned that the identification scheme set forth abovecould be used in conjunction with other means for identifying the typeof battery pack that is coupled to the battery charger.

With continued reference to FIGS. 4A-4C, another method for identifyingthe type of battery pack is described. In each of the packs, there is aterminal (designated as 4 v in the figures) that is coupled to ameasurement node disposed between the first battery cell and theremainder of the battery cells. By changing the location of thisterminal amongst the three different packs, the location of thisterminal can be used to identify the pack type.

Referring to FIG. 6, the charger control module 24 first measuresvoltage 61 at a plurality of designated terminals (e.g., terminals 3, 4,6 and 7) of the battery pack. Given the voltage measurements for eachdesignated terminal, the charger control module 24 determines at step 62which designated terminal has the lowest voltage measure. While theterminal with the lowest voltage measurement will be approximately 4volts in a fully charged condition, it is readily understood thatregardless of the stated charge of the pack 16 the lowest voltageterminal will be the same. The type of battery pack can then bedetermined based on the position of the lowest voltage terminal. It isenvisioned that this approach can be applied to one of the otherterminals, such as the terminal with the second lowest voltage measureor the terminal connected to the thermistor.

In the exemplary embodiment, when the charge control module 24determines at step 63 that terminal 4 has the lowest voltage measure,the battery charger is presumed to be coupled to the pack 16′ havingthree cells. The charge control module 24 in turn selects a chargingalgorithm at step 64 suitable for charging the pack 16′. Alternatively,the charge control module 24 may set parameters (e.g., an overchargevoltage threshold for the total pack) in a generic charging algorithmthat is suitable for the pack 16′. The charge control module can thencommerce charging in accordance with the appropriate charging algorithmas indicated at 69.

When the charge control module determines at 65 that designated terminal6 has the lowest voltage measure, the battery charger is presumed to becoupled to the pack 16″ having four cells. When the charge controlmodule determines at 67 that terminal 3 has the lowest voltage measure,the battery charger is presumed to be coupled to the pack 16′″ havingfive cells. In either case, the charge control module selects theappropriate charging algorithm 66, 68 for the identified battery packand commences charging as indicated at step 69.

While the identification schemes set forth above are used to determinethe nominal voltage of the battery pack, the scheme could be used toidentify other attributes of a battery pack. For instance, theidentification scheme could be used to distinguish between packs havingdifferent cell chemistry. Other types of attributes, such as cellchemistry, cell supplier or cell arrangement (i.e., number of parallelcell strings) are also contemplated by this disclosure. It is furthercontemplated that these identification schemes could be implemented by acontroller into a tool such that the tool identifies attributes of thebattery pack coupled thereto.

Referring to FIG. 7, a battery pack 100 includes a body 102 having agenerally rectangular shape, and can include a connection port 104extending from a rear face 106 used to connect battery pack 100 forcharging or to a tool (not shown) for use of the charge stored inbattery pack 100. Opposed first and second side walls 108, 110 areoriented perpendicular to the rear face 106. To assist in manuallyinstalling and/or removing battery pack 100 with respect to a rechargingdevice or a tool, a recessed, female finger notch 112 is provideddefining an opening into body 102 from a front face 114. Front face 114is substantially planar but may include fascia features, manufacturerlabels, instructions for use and recharging, battery pack ratings, andthe like, either embossed, recessed, stamped, tagged, or otherwiseprovided with front face 114.

According to several embodiments, finger notch 112 includes a lead-inwall 116 and an oppositely positioned engagement wall 118, which arejoined at a notch cavity bottom wall 120 recessed below the front face114. The lead-in wall 116 can define a convex-shaped curve directlyoutwardly. Finger notch 112 is employed by a user inserting one or morefingers (not shown) into finger notch 112 by initially sliding thefingers in a first operating direction “A” along front face 114 until alead-in edge 122 of lead-in wall 116 is encountered. The user's fingersthereafter enter downwardly (away from the viewer in FIG. 7) into fingernotch 112 and continue to slide along lead-in wall 116 until reachingboth bottom wall 120 and contacting engagement wall 118. Continuedpressure applied by the user's fingers in the first operating direction“A” is then transferred by direct contact substantially throughengagement wall 118 to displace battery pack 100 in the first operatingdirection “A”. Opposed finger notch end walls 126, 128 are orientedperpendicular to front face 114 and the notch cavity bottom wall 120,and parallel to each of the first and second side walls 108, 110. Notchend walls 126, 128 provide side-to-side limits to help retain the user'sfingers within finger notch 112.

Referring to FIG. 8, finger notch 112 is oriented substantiallyperpendicular to first and second side walls 108, 110, and finger notch112 has a total length “B” centered with respect to a longitudinal axis130 of battery pack 100. A total width “C” of finger notch 112 can beapproximately 15.2 mm to provide access for receiving the fingers theuser. A longitudinal axis 132 of bottom wall 120 locates finger notch112 approximately 30.2 mm from an end wall 134 of body 102 in oneexemplary embodiment. To assist the user in moving battery pack 100 in asecond operating direction “E”, which is oppositely directed withrespect to first operating direction “A”, at least one and according toseveral embodiments a plurality of contact members 136 can integrallyextend from front face 114 and can each include an extending portion 138extending partially into finger notch 112 past lead-in wall 116. Theuser's fingers will directly engage contact members 136 when the fingersare moved in the second operating direction “E” to assist in movingbattery pack in the second operating direction “E”. The above dimensionsrepresent one exemplary embodiment and are not intended to limit batterypack 100 or finger notches 112 of the present disclosure to any specificdimensions.

Referring to FIG. 9, to maximize user engagement with finger notch 112and the force transferred to battery pack 100 using finger notch 112 infirst operating direction “A”, a first pitch angle α or slope ofengagement wall 118 is substantially greater than a second pitch angle βor slope of lead-in wall 116. Engagement wall 118 is oriented at angle αof approximately 60 degrees with respect to front face 114. Lead-in wall116 is oriented at angle β of approximately 30 degrees with respect tofront face 114. According to several embodiments, first pitch angle α isapproximately double (2 times) or greater than second pitch angle β toensure user direct contact with engagement wall 118. Battery pack 140can also include multiple slots 140 sized to slidably receive and retainrechargeable batteries (not shown).

Referring to FIG. 10, a battery pack connection system 200 is used forelectrical connection of a plurality of individual battery cells 202,202′, 202″, 202′″, 202″″ of a battery pack 203. Battery pack connectionsystem 200 can include multiple individual battery cell wires, includinga first cell wire 204, a second cell wire 206, a third cell wire 208,and a fourth cell wire 210. Each of the individual cell wires arepre-formed of a substantially rigid material intended to retain apre-formed shape prior to, during and after installation in battery pack203. Each of the individual cell wires includes a pressure connectionend 212 that is partially deflected to bias pressure connection end 212into direct contact with a planar face 214 of a printed circuit board(PCB) contact pad 216. To maintain the pre-formed shape of each of theindividual cell wires, they are also retained in an installed positionby receipt in elongated slots or apertures of a connector member 218located proximate to printed circuit board contact pad 216, and also toslots of individual remote slotted members 220 located proximate to theconnection of the individual cell wires at its individual cell or cells.According to several embodiments, connector member 218 can be a singlemember retaining all of the individual cell wires, or can be individualmembers each retaining one or more of the cell wires.

Referring to FIG. 11, the slotted members 218 individually retain thefirst, second, third and fourth cell wires 204, 206, 208, 210 (onlyfirst cell wire 204 is clearly visible in this view) in an exemplaryembodiment connected to battery 202′. The pressure connection end 212 ofeach cell wire is formed as a bent or formed partial loop extending fromeach of the connector slotted members 218. Each pressure connection end212 includes a first portion 222 directly contacting the planar face 214of PCB contact pad 216, and a second portion 224 directed back towardbattery 202′. According to several embodiments, each pressure connectionend 212 defines a bend ranging from less than 90 degrees toapproximately 180 degrees.

Pressure connection ends 212 are intended to help mitigate againstvibration of battery pack 203 causing contact between first portion 222and planar face 214 of PCB contact pad 216 to become intermittent, forexample if battery pack or pressure connection end 212 vibration reachesa resonant frequency. To accomplish this function, each pressureconnection end 212 is created with a different spring constant for eachof the first and second portions 222, 224, or the first and secondportions 222, 224 can each have the same spring constant but a differentmass. The first spring constant of first portion 222 together with itsgeometry as a U-shaped bend results in a biasing force acting in a firstbiasing direction “G” created when first portion 222 elasticallydeflects when directly contacting planar face 214. Second portion 224has a second spring constant different than the first spring constant,or as noted above the first and second portions 222, 224 can each havethe same spring constant but a different mass. The second springconstant of second portion 224 results in a biasing force acting in asecond biasing direction “H” opposite to first biasing direction “G” andresulting when second portion 224 contacts battery or cell 202′. Aspacing dimension “J” between battery 202′ and planar face 214 ispredetermined such that if either first portion 222 or second portion224 of pressure connection end 212 vibrates at its natural frequency,contact will be maintained between pressure connection end 212 andplanar face 214 to maintain electrical connectivity.

Referring to FIG. 12 and again to FIG. 10, a battery pack connectionsystem 300 is used for electrical connection of a plurality ofindividual battery cells 302, 302′, 302″, 302′″, 302″″ of a battery pack303. Battery pack connection system 300, similar to battery packconnection system 200, can include multiple individual battery cellwires, including a first cell wire 304, a second cell wire 306, a thirdcell wire 308, and a fourth cell wire 310. Each of the individual cellwires are pre-formed of a substantially rigid material intended toretain a pre-formed shape prior to, during and after installation inbattery pack 303. Each of the individual cell wires includes a pressureconnection end 312 each inserted into one of a plurality of receivingapertures 314 of a polymeric connector 316. To maintain the pre-formedshape of each of the individual cell wires, they can also beindividually retained in an installed position by receipt in elongatedslots of individual connector slotted members 318 (only one is shown)similar to connector slotted members 218 each mounted to a printedcircuit board (PCB) connection member 320, and also to slots ofindividual remote slotted members 322, similar to remote slotted members220 and located proximate to the cell wire connection at the individualcells.

Referring to FIG. 13, pressure connection ends 312 are intended tomitigate against vibration of battery pack 303 causing contact betweenpressure connection ends 312 and a connection terminal 324 providingelectrical contact with (PCB) connection member 320 to becomeintermittent, for example if battery pack or pressure connection end 312vibration reaches a resonant frequency. To accomplish this goal, eachpressure connection end 312 is retained using two opposed biasingforces.

The following discussion of installation of pressure connection end 312′applies equally to each of the pressure connecting ends 312. The firstbiasing force is created when pressure connection end 312′ is insertedinto one of the receiving apertures 314′ of connector 316. The pressureconnection end 312′ is inserted in a direction “K” and received in acavity 326 created between a spring leg 328 of a generally U-shapedbiasing member 330 and a wall 332 of connector 316. This forces pressureconnecting end 312′ to elastically deflect in a first direction “L”which creates an opposite biasing force from connecting end 312′ actingin a second direction “M” maintaining direct contact between connectingend 312′ and spring leg 328. The second biasing force is provided byspring leg 328, which is elastically deflected in the second direction“M” when pressure connecting end 312′ is received, thereby creating abiasing force acting in the first direction “L”. A spring constant ofpressure connecting end 312′ and of spring leg 328 are different fromeach other, such that vibration causing deflection of either pressureconnecting end 312′ or spring leg 328 at a natural frequency of eitherone will not result in vibration at the natural frequency of the other.

Biasing member 330 further includes a connecting end 334 which is fixedto a leg 336 of the connection terminal 324. Connection terminal 324extends outwardly through an aperture 338 created through PCB connectionmember 320. A non-linear portion 340 can be positioned at leastpartially within aperture 338 to retain the position of connectionterminal 324. According to several embodiments, the connecting end 312of any of the plurality of cell wires 304, 306, 308, 310 is oriented atan angle α with respect to the cell wire. Angle α is preferably lessthan 90 degrees to permit only a free end 342 of the connecting end 312to contact wall 332 to help retain the biasing force of connecting end312.

The foregoing description of the embodiments has been provided forpurposes of illustration and description. It is not intended to beexhaustive or to limit the disclosure. Individual elements or featuresof a particular embodiment are generally not limited to that particularembodiment, but, where applicable, are interchangeable and can be usedin a selected embodiment, even if not specifically shown or described.The same may also be varied in many ways. Such variations are not to beregarded as a departure from the disclosure, and all such modificationsare intended to be included within the scope of the disclosure.

What is claimed is:
 1. A battery pack system, comprising: a set ofbattery packs, the set of battery packs including L battery packs, eachbattery pack of the set of battery packs including a different number Mof battery cells, where 2≦M≦N and where L≧2 and N>L, where N is a wholenumber; each battery pack of the set of battery packs including a set ofbattery terminals, each set of battery terminals including O batteryterminals, where O<N; each set of battery terminals including a firstsubset of battery terminals, wherein each first subset of batteryterminals has a different number P of battery terminals, where 0≦P<O,and each battery terminal of the first subset of battery terminals iscoupled to a first battery reference node, and each set of batteryterminals including a second subset of battery terminals, each secondsubset of battery terminals including Q battery terminals, where Q=O−P,and each battery terminal of the second subset of battery terminals iscoupled to a battery measurement node.
 2. The battery pack system ofclaim 1, wherein the first battery reference node is a battery positivevoltage node.
 3. The battery pack system of claim 1, wherein the batterymeasurement node is a node between battery cells.
 4. The battery packsystem of claim 1, wherein L=3 and N=5 and O=4.
 5. A battery packcomprising: a set of battery terminals, the set of battery terminalsincluding O battery terminals, a first subset of the set of batteryterminals, the first subset of battery terminals including P batteryterminals, where 0≦P<O, and each battery terminal of the first subset ofbattery terminals is coupled to a first battery reference node, and asecond subset of the set of battery terminals, the second subset ofbattery terminals including Q battery terminals, where Q=O−P, and eachbattery terminal of the second subset of battery terminals is coupled toa battery measurement node.
 6. The battery pack of claim 5, furthercomprising a set of battery cells, the set of battery cells including Mbattery cells and where 2≦M≦N and where N>O, where N is a whole number.7. The battery pack of claim 6, wherein N=5 and O=4.
 8. The battery packof claim 5, wherein the first battery reference node is a batterypositive voltage node.
 9. The battery pack of claim 5, wherein thebattery measurement node is a node between battery cells.
 10. A batterypack and battery charger platform, comprising: a set of battery packs,the set of battery packs including L elements, each battery pack of theset of battery packs including a different number M of battery cells,where 2≦M≦N and where L≧2 and N>L, where N is a whole number; eachbattery pack of the set of battery packs including a set of batteryterminals, the set of battery terminals including O battery terminals,where O<N; each set of battery terminals including a first subset ofbattery terminals, wherein each first subset of battery has a differentnumber of P battery terminals, where 0≦P<O, and each battery terminal ofthe first subset of battery terminals is coupled to a first batteryreference node; and each set of battery terminals including a secondsubset of battery terminals, each second subset of battery terminalsincluding Q battery terminals, where Q=O−P, and each battery terminal ofthe second subset of battery terminals is coupled to a batterymeasurement node; and a battery charger including a set of chargerterminals, the set of charger terminals including O charger terminals,the battery charger configured to mechanically couple to each batterypack in the set of battery packs such that each charger terminalmechanically and electrically couples to a corresponding batteryterminal, wherein the battery charger is configured to determine thenumber of battery cells in the battery pack coupled to the batterycharger based on P.